High Temperature Nitriding  of Titanium Parts

ABSTRACT

A method and apparatus for manufacturing a part. The part may be positioned in a chamber. The part may be comprised of a metal and may be a positioned part. A gas containing nitrogen may be sent into the chamber. An electromagnetic field may be generated in the chamber with the gas. The electromagnetic field may heat a portion of the metal in the positioned part to a temperature from about 60 percent to about 99 percent of the melting point of the metal such that the portion of the metal has a desired hardness. The portion of the metal may extend from a surface of the positioned part to a selected depth from the surface.

BACKGROUND INFORMATION

1. Field

The present disclosure relates generally to manufacturing parts and, inparticular, to a method and apparatus for manufacturing hardenedmetallic structures. Still more particularly, the present disclosurerelates to a method and apparatus for manufacturing a titanium parthaving a desired case thickness.

2. Background

A structure formed using titanium parts may have a reduced weight ascompared to a structure formed using parts comprised of other types ofmetals or metal alloys. For example, without limitation, titanium partsmay provide an increased strength to weight advantage over steel.However, titanium parts may not have the surface hardness desired forapplications that involve the rubbing of two titanium surfaces againsteach other. For example, without limitation, titanium surfaces may beprone to undesired effects, such as galling, scoring, and/or fretting.

These undesired effects may be prevented using a number of differentmethods including, without limitation, nitriding. With nitriding,nitrogen may be introduced into a portion of the titanium part through,for example, without limitation, diffusion. This introduction ofnitrogen into the titanium part may produce a layer on the surface ofthe titanium part comprising, without limitation, titanium nitrides.This layer may be referred to as a case for the titanium part.

Currently available processes for nitriding titanium may form cases thathave a depth of about 0.005 inches or less. However, with cases of thesedepths, the titanium parts may not be capable of carrying larger appliedloads. In other words, these case depths may be too thin to allow thetitanium parts to carry larger applied loads.

For example, without limitation, titanium parts may take the form ofgears, bearings, shafts, rods, and/or other suitable types of parts.Applications using these parts, such as, for example, withoutlimitation, gear or bearing applications, may result in applied loads totitanium parts that may produce surface and sub-surface stresses in thetitanium part. Currently available processes of nitriding may notprovide a case depth that is deep enough to prevent these undesiredstresses in the case. Additionally, currently available processes ofnitriding may not be able to form cases of a sufficient depth forcounteracting surface contact stresses, bending stresses, sub-surfaceshear stresses, and/or other undesired effects.

Therefore, it would be advantageous to have a method and apparatus thattakes into account one or more of the issues discussed above, as well aspossibly other issues.

SUMMARY

In one advantageous embodiment, a method may be provided formanufacturing a part. The part may be positioned in a chamber. The partmay be comprised of a metal. A gas containing nitrogen may be sent intothe chamber. An electromagnetic field may be generated in the chamberwith the gas. The electromagnetic field may heat a portion of the metalin the positioned part to a temperature from about 60 percent to about99 percent of a melting point of the metal. The portion of the metal mayextend from a surface of the positioned part to a selected depth fromthe surface.

In another advantageous embodiment, a method may be provided for forminga case on a titanium part. The titanium aircraft part may be positionedin a chamber. The titanium part may be comprised of a metal and may be apositioned part. The metal may be selected from a group comprisingtitanium and a titanium alloy. The titanium part may be selected from agroup comprising a gear, a bearing, a crankshaft, a camshaft, a camfollower, a valve, an extruder screw, a die, a bushing, a pin, and aninjector. A vacuum may be applied in the chamber. After removing all airfrom the chamber, a gas containing nitrogen may be sent into the chamberto generate a pressure of up to about 150 pounds per square inch insidethe chamber. An electromagnetic field may be generated in the chamberwith the gas for up to about 30 minutes. The electromagnetic field mayhave a first frequency and a second frequency. The electromagnetic fieldmay heat a first portion of the metal in the positioned part to atemperature from about 60 percent to about 99 percent of a melting pointof the metal such that the first portion of the metal may have a desiredhardness while reducing changes to mechanical properties of thepositioned part below the selected depth in a second portion of themetal. The first portion of the metal may extend from a surface of thepositioned part to a selected depth from the surface. The selected depthmay be about 0.005 inches or greater. The first portion may be a casefor the positioned part.

In yet another advantageous embodiment, an apparatus may comprise achamber, a gas delivery system, and an induction coil system. Thechamber may be configured to hold a part as a positioned part. The partmay be comprised of a metal. The gas delivery system may be configuredto send a gas containing nitrogen into the chamber. The induction coilsystem may be configured to generate an electromagnetic field inside thechamber. The electromagnetic field may heat a portion of the metal inthe positioned part in the chamber to a temperature from about 60percent to about 99 percent of a melting point of the metal. The portionof the metal may extend from a surface of the positioned part to aselected depth from the surface.

In still yet another advantageous embodiment, a heat system may comprisea chamber, a gas delivery system, an induction coil system, a powerunit, and a controller. The chamber may be configured to hold a part asa positioned part. The part may be comprised of a metal selected from agroup comprising titanium and a titanium alloy. The part may be selectedfrom a group comprising a gear, a bearing, a crankshaft, a camshaft, acam follower, a valve, an extruder screw, a die, a bushing, a pin, andan injector. The gas delivery system may be configured to send a gascontaining nitrogen into the chamber.

The gas containing the nitrogen in the chamber may have a pressure of upto about 150 pounds per square inch inside the chamber. The inductioncoil system may be configured to generate an electromagnetic fieldinside the chamber. The electromagnetic field may have a first frequencyand a second frequency. The electromagnetic field may heat a firstportion of the metal in the positioned part in the chamber to atemperature from about 60 percent to about 99 percent of a melting pointof the metal such that the first portion of the metal may have a desiredhardness while reducing undesired changes to mechanical properties ofthe positioned part below the selected depth in a second portion of themetal. The first portion of the metal may extend from a surface of thepositioned part to a selected depth from the surface. The first portionmay be a case for the positioned part. The selected depth may be about0.005 inches or greater. The power unit may be configured to generate acurrent that causes the induction coil system to generate theelectromagnetic field inside the chamber. The controller may beconfigured to cause the induction coil system to heat the positionedpart in the chamber with the gas for up to about 30 minutes.

The features, functions, and advantages can be achieved independently invarious embodiments of the present disclosure or may be combined in yetother embodiments in which further details can be seen with reference tothe following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the advantageousembodiments are set forth in the appended claims. The advantageousembodiments, however, as well as a preferred mode of use, furtherobjectives, and advantages thereof, will best be understood by referenceto the following detailed description of an advantageous embodiment ofthe present disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of an aircraft manufacturing and servicemethod in accordance with an advantageous embodiment;

FIG. 2 is an illustration of an aircraft in which an advantageousembodiment may be implemented;

FIG. 3 is an illustration of a block diagram of a manufacturingenvironment in accordance with an advantageous embodiment;

FIG. 4 is an illustration of a heating system in accordance with anadvantageous embodiment;

FIG. 5 is an illustration of a cross-sectional top view of a chamber ina heating system in accordance with an advantageous embodiment;

FIG. 6 is an illustration of a cross-sectional view of a portion of agear in accordance with an advantageous embodiment;

FIG. 7 is an illustration of a table of test results from heating a partin accordance with an advantageous embodiment; and

FIG. 8 is an illustration of a flowchart of a process for manufacturinga part in accordance with an advantageous embodiment.

DETAILED DESCRIPTION

Referring more particularly to the drawings, embodiments of thedisclosure may be described in the context of aircraft manufacturing andservice method 100 as shown in FIG. 1 and aircraft 200 as shown in FIG.2. Turning first to FIG. 1, an illustration of an aircraft manufacturingand service method is depicted in accordance with an advantageousembodiment. During pre-production, aircraft manufacturing and servicemethod 100 may include specification and design 102 of aircraft 200 inFIG. 2 and material procurement 104.

During production, component and subassembly manufacturing 106 andsystem integration 108 of aircraft 200 in FIG. 2 may take place.Thereafter, aircraft 200 in FIG. 2 may go through certification anddelivery 110 in order to be placed in service 112. While in service 112by a customer, aircraft 200 in FIG. 2 may be scheduled for routinemaintenance and service 114, which may include modification,reconfiguration, refurbishment, and other maintenance or service.

Each of the processes of aircraft manufacturing and service method 100may be performed or carried out by a system integrator, a third party,and/or an operator. In these examples, the operator may be a customer.For the purposes of this description, a system integrator may include,without limitation, any number of aircraft manufacturers andmajor-system subcontractors; a third party may include, withoutlimitation, any number of venders, subcontractors, and suppliers; and anoperator may be an airline, leasing company, military entity, serviceorganization, and so on.

With reference now to FIG. 2, an illustration of an aircraft is depictedin which an advantageous embodiment may be implemented. In this example,aircraft 200 is produced by aircraft manufacturing and service method100 in FIG. 1 and may include airframe 202 with a plurality of systems204 and interior 206. Examples of systems 204 include one or more ofpropulsion system 208, electrical system 210, hydraulic system 212, andenvironmental system 214. Any number of other systems may be included.Although an aerospace example is shown, different advantageousembodiments may be applied to other industries, such as the automotiveindustry.

Apparatus and methods embodied herein may be employed during at leastone of the stages of aircraft manufacturing and service method 100 inFIG. 1. As used herein, the phrase “at least one of”, when used with alist of items, means that different combinations of one or more of thelisted items may be used and only one of each item in the list may beneeded. For example, “at least one of item A, item B, and item C” mayinclude, for example, without limitation, item A or item A and item B.This example also may include item A, item B, and item C or item B anditem C.

In one illustrative example, components or subassemblies produced incomponent and subassembly manufacturing 106 in FIG. 1 may be fabricatedor manufactured in a manner similar to components or subassembliesproduced while aircraft 200 is in service 112 in FIG. 1. As yet anotherexample, a number of apparatus embodiments, method embodiments, or acombination thereof may be utilized during production stages, such ascomponent and subassembly manufacturing 106 and system integration 108in FIG. 1. A number, when referring to items, means one or more items.For example, a number of apparatus embodiments may be one or moreapparatus embodiments. A number of apparatus embodiments, methodembodiments, or a combination thereof may be utilized while aircraft 200is in service 112 and/or during maintenance and service 114 in FIG. 1.The use of a number of the different advantageous embodiments maysubstantially expedite the assembly of and/or reduce the cost ofaircraft 200.

The different advantageous embodiments recognize and take into account anumber of different considerations. For example, without limitation, thedifferent advantageous embodiments recognize and take into account thatusing titanium as a material for a part, such as a gear or bearing, mayprovide a good lightweight and high-strength part. In other words, theweight and strength of the part may be at a desired level for aparticular use. A lighter weight, as compared to other currentmaterials, may be desirable, especially in aircraft.

The different advantageous embodiments also recognize and take intoaccount that titanium may be softer than other metals, such as steel. Asa result, two titanium parts may adhere to each other during use. Inother words, the two parts may not slide with respect to each other assmoothly as desired. This situation may occur when the coefficient offriction may become large enough such that surfaces between the twoparts may require more force to slide with respect to each other. As aresult, the friction between the two surfaces of the parts may be largeenough to require greater forces than desired to cause the surfaces toslide with respect to each other.

The different advantageous embodiments recognize and take into accountthat one solution may involve forming a hardened case on the titaniumparts. The case may be formed having a hardness that reduces thefriction that the titanium part encounters when turning against anotherpart. The different advantageous embodiments recognize and take intoaccount that this case may be formed on the surface of the gear. Thecase may extend from the surface down to some selected depth. The depthbelow the surface may vary.

The different advantageous embodiments recognize and take into accountthat it may be desirable to have a thicker case than currentlyavailable. Currently available processes may provide a case on atitanium part that may be about 0.005 inches or less. The creation ofthis case may be through a nitriding process used on the titanium. Thenitriding process may introduce nitrogen into the surface of the metalto create a hardened surface. By introducing nitrogen into the metal, alayer or section of a harder alloy may be formed.

The different advantageous embodiments recognize and take into accountthat cases of this thickness may not be suitable for some types ofparts. For example, without limitation, with gears and bearings, use mayoccur in which loads may create stresses in the gear. These stresses maycause undesired features to occur to the case. For example, withoutlimitation, the loads may have undesired effects on the case. Thesetypes of features may reduce the life of a gear. As a result, thedifferent advantageous embodiments recognize and take into account thatthe object, such as an aircraft in which a gear is used, may requiremore maintenance than desired and may encounter increased costs.

The different advantageous embodiments recognize and take into accountthat currently used processes for nitriding titanium may take more timethan desired. For example, without limitation, one process may involveplasma carburizing to form a case for a part. Plasma carburizing may usea plasma furnace at a temperature of about 700 degrees centigrade toabout 1100 degrees centigrade for about three hours. This type ofprocess may result in a case having a depth of about 0.00275 inches.

Currently available processes for forming cases for parts may not beable to provide the desired depths for the cases. For example, withoutlimitation, currently available processes for nitriding may be unable toform a case that has a depth of about 0.005 inches or greater.

Further, the different advantageous embodiments recognize and take intoaccount that currently available processes for nitriding titanium partsthat use furnaces may expose substantially the entire titanium part tothe nitriding temperatures. As a result, undesired changes to themechanical properties of the part below the case formed by nitriding mayoccur. For example, without limitation, the part may have a strengthlower than desired below the case. Further, the size of the grains inthe part below the case may increase undesirably.

The different advantageous embodiments recognize and take into accountthat nitriding titanium parts, by exposing only a portion of the part tothe nitriding temperatures as compared to the entire part, may reduceand/or prevent undesired changes in the part. For example, withoutlimitation, exposing the surface of the part to the nitridingtemperatures as compared to the entire part may reduce undesireddecreases in the strength of the part below the case.

Thus, the different advantageous embodiments provide a method andapparatus for manufacturing a part. A part may be positioned in achamber in which the part may be comprised of metal. A gas containingnitrogen may be sent into the chamber. An electromagnetic field may begenerated in the chamber with the gas. The electromagnetic field mayheat a portion of the metal in the positioned part in which the portionmay extend from a surface of the part to a selected depth from thesurface. The electromagnetic field may heat the portion to a temperaturefrom about 60 percent to about 99 percent of the melting point of themetal such that the portion may have a desired hardness, while reducingundesired changes to mechanical properties of the part below theselected depth.

With reference now to FIG. 3, an illustration of a block diagram of amanufacturing environment is depicted in accordance with an advantageousembodiment. Manufacturing environment 300 may be used to manufactureparts of an aircraft, such as, for example, without limitation, aircraft200 in FIG. 2.

In this illustrative example, manufacturing environment 300 may be usedto process part 302. Part 302 may be comprised of metal 304. In theseillustrative examples, part 302 may take a number of different forms.For example, without limitation, part 302 may be a part selected from agroup comprising a gear, a bearing, a crankshaft, a camshaft, a camfollower, a valve, an extruder screw, a die, a bushing, a pin, aninjector, and/or other suitable types of parts. Metal 304 also may takea number of different forms. For example, without limitation, metal 304may be selected from a group comprising titanium, a titanium alloy,and/or other suitable types of metals.

In these illustrative examples, part 302 may be processed using heatingsystem 306. Heating system 306 may comprise induction heater 308, gassystem 310, vacuum system 312, chamber 314, and/or other suitablecomponents. In this illustrative example, induction heater 308 mayinclude power unit 316 and coil system 318. Coil system 318 may includenumber of coils 320.

In these illustrative examples, power unit 316 may cause coil system 318to generate electromagnetic field 322. Electromagnetic field 322 mayhave number of frequencies 324. In the illustrative examples, number offrequencies 324 may be one frequency, two frequencies, or some othernumber of frequencies. Number of frequencies 324 may have differentvalues. For example, without limitation, when metal 304 is titanium,number of frequencies 324 may be from about eight kilohertz to about 450kilohertz. In this illustrative example, number of frequencies 324 maybe two frequencies to provide dual frequency induction heating byinduction heater 308.

As depicted, chamber 314 may include housing 326 and part holder 328.Part holder 328 may be located inside of housing 326 and may beconfigured to hold part 302 inside of housing 326.

Gas system 310 may include gas supply unit 330 and gas delivery system332. Gas delivery system 332 may deliver gas 334 containing nitrogen 336from gas supply unit 330 to chamber 314. Gas 334 containing nitrogen 336may be delivered into chamber 314 after vacuum system 312 creates vacuum338 inside of chamber 314. In this illustrative example, vacuum system312 may create vacuum 338 to remove substantially all of air 339 inchamber 314. Air 339 comprises oxygen in these illustrative examples.

In these illustrative examples, part 302 may be positioned withinchamber 314 as positioned part 340. Part 302 may be positioned usingpart holder 328.

With positioned part 340 within chamber 314, gas system 310 may send gas334 containing nitrogen 336 into chamber 314 such that pressure 342 maybe generated within chamber 314. Pressure 342 may be, for example,without limitation, up to about 150 pounds per square inch or about 10bar inside chamber 314. In other illustrative examples, higher pressuresmay be used.

With gas 334 containing nitrogen 336 and having pressure 342 inside ofchamber 314, electromagnetic field 322 may be generated such thatelectromagnetic field 322 may heat portion 344 of part 302. Portion 344may extend from surface 348 of positioned part 340 to selected depth 346from surface 348. In other words, selected depth 346 may be some depthbelow surface 348. Selected depth 346, in these illustrative examples,may be about 0.005 inches or greater.

Selected depth 346 may be selected through the generation ofelectromagnetic field 322. Various parameters, such as frequency, numberof frequencies, time, and/or other suitable parameters, may be selectedto cause heating within portion 344 to selected depth 346 in positionedpart 340.

For example, without limitation, number of frequencies 324 may beselected to heat portion 344 to selected depth 346. In theseillustrative examples, this type of heating of positioned part 340 maybe induction heating 350. Induction heating 350 may be a process ofheating portion 344 in which eddy currents 352 may be generated withinportion 344. Resistance of metal 304 within portion 344 may lead toheating of metal 304 within portion 344.

Further, number of frequencies 324 may be selected such that inductionheating 350 occurs substantially for portion 344 of metal 304 but notsubstantially for portions of metal 304 below portion 344. Otherportions of metal 304 below portion 344 may be heated throughconduction. This type of heating may not occur for a period of time longenough to cause undesired changes in the portions of metal 304 belowportion 344.

In these illustrative examples, the heating of portion 344 in positionedpart 340 may be such that desired temperature 354 is reached withinportion 344. Desired temperature 354 may have range 356. In theseexamples, desired temperature 354 may be maintained at a particulartemperature within range 356 or varied during heating of portion 344 inpositioned part 340.

Range 356, in these examples, may be, for example, without limitation,from about 60 percent to about 99 percent of melting point 305 of metal304. As one illustrative example, when metal 304 is titanium, range 356may be from about 1,000 degrees Celsius to about 1,600 degrees Celsius.

In these illustrative examples, the heating may be such that portion 344has desired hardness 358. Portion 344 may have nitrogen 336 from gas 334in portion 344. The presence of nitrogen 336 within portion 344 maygenerate alloy 360. In these illustrative examples, portion 344 may formcase 370 in positioned part 340. Number of frequencies 324 may beselected to provide selected depth 346 for case 370.

The heating of portion 344 to create desired hardness 358 may beperformed while reducing undesired changes 361 to mechanical properties362 of positioned part 340 below selected depth 346. As one illustrativeexample, undesired changes 361 to portion 364 below or further in fromsurface 348 below selected depth 346 may include an undesired increasein grain size 366 in portion 364. Increasing grain size 366 may resultin a decrease in time before undesired effects occur within portion 364.

In these illustrative examples, heating of positioned part 340 may occurfor period of time 372. For example, without limitation, period of time372 may be from about one minute to about 30 minutes or more. In otherillustrative examples, period of time 372 may be, for example, withoutlimitation, about an hour.

Additionally, period of time 372 may be a continuous or discontinuousperiod of time. For example, without limitation, in one illustrativeexample, positioned part 340 may be heated continuously for about 30minutes. In another illustrative example, positioned part 340 may beheated six different times for about 5 minutes each time to heatpositioned part 340 for about 30 minutes.

The illustration of manufacturing environment 300 in FIG. 3 is not meantto imply physical or architectural limitations to the manner in whichdifferent advantageous embodiments may be implemented. Other componentsin addition to and/or in place of the ones illustrated may be used. Somecomponents may be unnecessary in some advantageous embodiments. Also,the blocks are presented to illustrate some functional components. Oneor more of these blocks may be combined and/or divided into differentblocks when implemented in different advantageous embodiments.

For example, in some advantageous embodiments, vacuum system 318 may notbe present in heating system 306. In other words, vacuum system 318 maynot be used to create vacuum 338 for chamber 314. In these advantageousembodiments, chamber 314 may be an air-tight chamber. Further, airremoval system 351 may be used in the place of vacuum system 318 toremove substantially all of air 339 in chamber 314.

Further, in some advantageous embodiments, part 302 may be manufacturedfor use with other objects, other than aircraft 200 in FIG. 2. Forexample, part 302 may be used in a spacecraft, a satellite, a submarine,a surface ship, an automobile, a tank, a truck, a power plant, anelevator system, and/or other suitable types of objects.

With reference now to FIG. 4, an illustration of a heating system isdepicted in accordance with an advantageous embodiment. In thisillustrative example, heating system 400 may be an example of oneimplementation for heating system 306 in FIG. 3.

In this illustrative example, heating system 400 may include powersupply 402, inert gas supply 404, chamber 406, induction coil 408,cooling ring manifold 410, part holder 412, and vacuum pump 414. Inertgas supply 404 may be connected to cooling ring manifold 410, which maybe nested within induction coil 408. Induction coil 408 may be connectedto power supply 402.

Inert gas supply 404 may supply inert gas 416 into interior 418 ofchamber 406, while induction coil 408 may generate electromagnetic field420. Vacuum pump 414 may create vacuum 422 within chamber 406. Further,gas supply 404 may introduce gas 416 into interior 418 of chamber 406with pressure 424.

With reference now to FIG. 5, an illustration of a cross-sectional topview of a chamber in a heating system is depicted in accordance with anadvantageous embodiment. As depicted, part 500 may be an example ofpositioned part 340 in FIG. 3. As depicted, part 500 may take the formof gear 502 and may be positioned within interior 418 of chamber 406 onpart holder 412. Gas 504 may be within interior 418 of chamber 406,while electromagnetic field 508 may be generated to heat gear 502.Surface 506 may include tooth surfaces of gear 502.

With reference now to FIG. 6, an illustration of a cross-sectional viewof a portion of a gear is depicted in accordance with an advantageousembodiment. In this illustrative example, gear 600 may be an example ofpositioned part 340 after being heated using heating system 306 in FIG.3.

In this illustrative example, gear 600 may have tooth 602 on wheel 604.Gear 600 may have portion 606 and portion 608. Portion 608 may take theform of case 610. Portion 608 may be an interior portion of gear 600.

In these illustrative examples, case 610 may extend from surface 612 ofgear 600 to depth 616. Depth 616 may be thickness 618 for case 610. Inthese illustrative examples, case 610 may have thickness 618 equal toabout 0.005 inches or greater.

Case 610 may take the form of hardened case 611 in this illustrativeexample. Hardened case 611 may be formed from portion 608 of gear 600through the use of heating system 306 in FIG. 3. Hardened case 611 mayprovide increased wear resistance for gear 600 and may allow gear 600 tocarry increased loads.

As depicted in this example, gear 600 may be inductively heated suchthat case 610 is formed for tooth 602 and for portion 620 and portion622 of wheel 604. However, in other illustrative examples, tooth 602 maybe inductively heated using heating system 306 in FIG. 3 such that case610 is not formed on portion 620 and portion 622 of wheel 604. In otherwords, heating system 306 in FIG. 3 may be used to inductively heat gear600 such that only portions of surface 612 are heated to depth 616.

With reference now to FIG. 7, an illustration of a table of test resultsfrom heating a part is depicted in accordance with an advantageousembodiment. In this illustrative example, table 700 may include testresults 701 from heating a part using heating system 306 in FIG. 3.

As depicted, table 700 may include test results 701 for test 1 702, test2 704, test 3 706, and test 4 708. The conditions for testing mayinclude temperature 710 at time 712.

The results of testing may include surface hardness 714 and effectivecase depth 716. Surface hardness 714 may be measured using RockwellSuperficial Hardness Testing, such as H15N, as specified by the AmericanSociety for Testing and Materials (ASTM) E18. Further, surface hardness714 may be approximately converted to the Rockwell C scale HRC inhardness 718. Additionally, effective case depth 716 may be measured fora specific hardness using a Vickers Hardness Tester, as specified by theAmerican Society for Testing and Materials E 384.

With reference now to FIG. 8, an illustration of a flowchart of aprocess for manufacturing a part is depicted in accordance with anadvantageous embodiment. The process illustrated in FIG. 8 may beimplemented using heating system 306 to manufacture part 302 in FIG. 3.

The process may begin by positioning part 302 in chamber 314 (operation800). Part 302 may be positioned part 340 after being positioned withinchamber 314. Part 302 may be positioned by part holder 328 in chamber314. In this illustrative example, part 302 may be comprised of metal304.

Thereafter, the process may remove substantially all of air 339 inchamber 314 (operation 802). Operation 802 may be performed by applyingvacuum 338 in chamber 314 using vacuum system 312, or by using airremoval system 351. In these examples, air 339 comprises oxygen.

The process may then send gas 334 containing nitrogen 336 into chamber314 to generate pressure 342 in chamber 314 (operation 804). Inoperation 804, gas 334 may be sent to chamber 314 by gas system 310. Inthis illustrative example, pressure 342 may be up to about 150 poundsper square inch or about 10 bar inside chamber 314.

Then, the process may generate electromagnetic field 322 in chamber 314with gas 334 in chamber 314 to heat part 302 (operation 806), with theprocess terminating thereafter. Operation 806 may be performed for up toabout 30 minutes in this illustrative example. Electromagnetic field 322may heat portion 344 of metal 304 to desired temperature 354. Portion344 may extend from surface 348 to selected depth 346. Further, desiredtemperature 354 may be about 60 percent to about 99 percent of meltingpoint of metal 304 in this illustrative example.

Additionally, electromagnetic field 322 may heat portion 344 such thatportion 344 may have desired hardness 358 while reducing undesiredchanges 361 to mechanical properties 362 of portion 364 below selecteddepth 346. For example, without limitation, increases in grain size 366in portion 364 may be reduced.

The flowchart and block diagrams in the different depicted embodimentsillustrate the architecture, functionality, and operation of somepossible implementations of apparatus and methods in differentadvantageous embodiments. In this regard, each block in the flowchart orblock diagrams may represent a module, segment, function, and/or aportion of an operation or step. In some alternative implementations,the function or functions noted in the block may occur out of the ordernoted in the figures. For example, in some cases, two blocks shown insuccession may be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. Also, other blocks may be added in addition tothe illustrated blocks in a flowchart or block diagram.

Thus, the different advantageous embodiments provide a method andapparatus for manufacturing a part. A part may be positioned in achamber in which the part may be comprised of metal and may be apositioned part after being positioned. A gas containing nitrogen may besent into the chamber. An electromagnetic field may be generated in thechamber with the gas. The electromagnetic field may heat a portion ofthe metal in the positioned part in which the portion may extend from asurface of the part to a selected depth from the surface. Theelectromagnetic field may heat the portion to a temperature from about60 percent to about 99 percent of the melting temperature of the metalsuch that the portion may have a desired hardness, while reducingchanges to mechanical properties of the part below the selected depth.

The description of the different advantageous embodiments has beenpresented for purposes of illustration and description and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different advantageousembodiments may provide different advantages as compared to otheradvantageous embodiments.

The embodiment or embodiments selected are chosen and described in orderto best explain the principles of the embodiments, the practicalapplication, and to enable others of ordinary skill in the art tounderstand the disclosure for various embodiments with variousmodifications as are suited to the particular use contemplated.

1. A method for manufacturing a part, the method comprising: positioningthe part in a chamber in which the part is comprised of a metal; sendinga gas containing nitrogen into the chamber; and generating anelectromagnetic field in the chamber with the gas in which theelectromagnetic field heats a portion of the metal in the positionedpart, in which the portion of the metal extends from a surface of thepositioned part to a selected depth from the surface, to a temperaturefrom about 60 percent to about 99 percent of a melting point of themetal.
 2. The method of claim 1, wherein the portion of the metal has adesired hardness while reducing undesired changes to mechanicalproperties of the positioned part below the selected depth.
 3. Themethod of claim 2, wherein the step of generating the electromagneticfield in the chamber with the gas in which the electromagnetic fieldheats the portion of the metal in the positioned part, in which theportion of the metal extends from the surface of the positioned part tothe selected depth from the surface, to the temperature from about 60percent to about 99 percent of the melting point of the metal such thatthe portion of the metal has the desired hardness while reducing theundesired changes to the mechanical properties of the positioned partbelow the selected depth comprises: generating the electromagnetic fieldin the chamber with the gas in which the electromagnetic field has afirst frequency and a second frequency and in which the electromagneticfield heats the portion of the metal in the positioned part, in whichthe portion of the metal extends from the surface of the positioned partto the selected depth from the surface, to the temperature from about 60percent to about 99 percent of the melting point of the metal such thatthe portion of the metal has the desired hardness while reducing theundesired changes to the mechanical properties of the positioned partbelow the selected depth.
 4. The method of claim 2, wherein the step ofgenerating the electromagnetic field in the chamber with the gas inwhich the electromagnetic field heats the portion of the metal in thepositioned part, in which the portion of the metal extends from thesurface of the positioned part to the selected depth from the surface,to the temperature from about 60 percent to about 99 percent of themelting point of the metal such that the portion of the metal has thedesired hardness while reducing the undesired changes to the mechanicalproperties of the positioned part below the selected depth comprises:generating the electromagnetic field in the chamber with the gas for upto about 30 minutes in which the electromagnetic field heats the portionof the metal in the positioned part and in which the portion of themetal extends from the surface of the positioned part to the selecteddepth from the surface, to the temperature from about 60 percent toabout 99 percent of the melting point of the metal such that the portionof the metal has the desired hardness while reducing the undesiredchanges to the mechanical properties of the positioned part below theselected depth.
 5. The method of claim 1, wherein the step of sendingthe gas containing the nitrogen into the chamber comprises: sending thegas containing the nitrogen into the chamber to generate a pressure ofup to about 150 pounds per square inch inside the chamber.
 6. The methodof claim 1 further comprising: removing substantially all air from thechamber prior to sending the gas containing the nitrogen into thechamber.
 7. The method of claim 6, wherein the step of removingsubstantially all of the air from the chamber prior to sending the gascontaining the nitrogen into the chamber comprises: removingsubstantially all the air from the chamber using at least one of avacuum system and an air removal system.
 8. The method of claim 1,wherein the portion of the metal is a first portion and wherein thefirst portion is a case for the positioned part and an undesiredincrease in a size of grains in a second portion of the positioned partbelow the case is reduced.
 9. The method of claim 1, wherein the chambercomprises a vacuum chamber.
 10. The method of claim 1, wherein theselected depth is about 0.005 inches or greater.
 11. The method of claim1, wherein the metal is selected from the group comprising consisting oftitanium and a titanium alloy.
 12. The method of claim 1, wherein thepart is selected from the group comprising consisting of a gear, abearing, a crankshaft, a camshaft, a cam follower, a valve, an extruderscrew, a die, a bushing, a pin, and an injector.
 13. A method forforming a case on a titanium part, the method comprising: positioningthe titanium part in a chamber in which the titanium part is comprisedof a metal and is a positioned part, in which the metal is selected froma group comprising titanium and a titanium alloy and in which thetitanium part is selected from a group comprising a gear, a bearing, acrankshaft, a camshaft, a cam follower, a valve, an extruder screw, adie, a bushing, a pin, and an injector; after removing all air from thechamber, sending a gas containing nitrogen into the vacuum chamber afterapplying the vacuum in the vacuum chamber to generate a pressure of upto about 150 pounds per square inch inside the vacuum chamber; andgenerating an electromagnetic field in the chamber with the gas for upto about 30 minutes in which the electromagnetic field has a firstfrequency and a second frequency, in which the electromagnetic fieldheats a first portion of the metal in the positioned part to atemperature from about 60 percent to about 99 percent of a melting pointof the metal such that the first portion of the metal has a desiredhardness while reducing undesired changes to mechanical properties ofthe positioned part below a selected depth in a second portion of themetal in which the first portion of the metal extends from a surface ofthe positioned part to the selected depth from the surface, the selecteddepth is about 0.005 inches or greater, and the first portion is thecase for the positioned part. 14-28. (canceled)